The T cell lymphokine that stimulates B cell maturation into PFC will be further purified and characterized. Antisera will be used to study reaction of the lymphokine with B cells. The uptake of 45 Ca ions by lymphocytes induced by concanavalin A, wheat germ mitogen or potato lectin will be compared. The effects of in vivo injection of concanavalin A, wheat germ mitogen and potato lectin on induction of T dependent and T independent responses will be compared.